SACCHARINE PRODUCTS. 47 



with 150 cc of 10 per cent alcohol, and finally with 20 cc of strong alcohol. Transfer 

 the residue to a large flask and boil gently for 4 hours with 200 cc of water and 20 cc 

 hydrochloric acid (specific gravity 1.125), the flask being provided with a reflux 

 condenser. Cool, neutralize with sodium hydroxid, add 5 cc of alumina cream, and 

 make up the volume to 250 cc with water. Filter, and determine the dextrose in an 

 aliquot part of the filtrate by Allihn's method, as directed in 13, page 49. The weight 

 of the dextrose multiplied by 0.9 gives the weight of the starch. 



10. POLARIZATION. 



(a) MOLASSES. 



Dissolve the normal weight of the sample (26.048 grams for the Schmidt and 

 Haensch polariscope) in water in a 100-cc graduated flask, add an excess of lead sub- 

 acetate solution,* and fill to the mark; shake to insure uniform solution, filter and 

 polarize in a 100-mm tube, multiplying the reading by 2 for the direct polarization. 



To 50 cc of the filtrate add 5 cc of concentrated hydrochloric acid. Heat slowly 

 to 68 and cool. Polarize in the same tube at the same temperature as before, add 

 10 per cent to the reading, and multiply by 2 for the invert polarization. 



The short tube (100-mm) is preferred for polarizing molasses not only on account 

 of the more or less deep color of the clarified solution, but also because a molasses 

 sample containing considerable commercial glucose would not read within the scale 

 limits if the 200-nini tube were employed. 



It sometimes happens, especially with molasses containing much glucose sirup, 

 that it is impossible to obtain a clear filtrate after clarification with lead subacetate, 

 or that the filtrate, at first Hear, clouds up too quickly to admit of a satisfactory 

 reading. In such cases weigh out a fresh portion of the sample, dilute, and add first 

 the lead subacetate solution ami then enough sodium sulphate or common salt to 

 pn-cipitate the excess of lead. Afterwards fill to the mark and proceed in the 

 regular manner. 



For medium or light-colored grades of molasses which yield but a small precipitate 

 with lead subacetate, the above method of simple polarization both direct and invert 

 gives results sufficiently accurate for ordinary work. For dark-colored or "black 

 strap" molasses, or wherever extreme accuracy is required, employ the double- 

 dilution method 10 (c). 



(b) HONEY, MAPLE SIRUP, AND WATER-SOLUBLE CONFECTIONERY. 



Follow directions given under "molasses," 10 (a), except that alumina cream b 

 is employed in excess as a clarifier instead of subacetate of lead. 



(c) CONFK(TIOXEKY CONTAINING STARCH OR INSOLUBLE MATTER. 



Employ the double-dilution method, c thus making due allowance for the volume 

 of the precipitate. Take half the normal weight of the sample and make up the 

 solution to 100 cc, using the appropriate elarilier (subacetate of lead for dark-colored 

 confectionery or molasses, and alumina cream for light -colored confectionery and 

 honey) . Take the normal weight of the sample and make up a second solution with 

 the clarifier to 100 cc. Filter and obtain direct polariscopic readings of both solu- 

 tions. Invert each in the usual manner and obtain the invert readings of the two. 



The true direct polarization of the sample is the product of the two direct readings 

 divided by their difference. The true invert polarization is the product of the two 

 invert readings divided by their difference. 



Sec footnote, page 84. 



11 Prepare by dividing n cold saturated aqueous solution of iiluni into two unequal portions, to the 

 larger of which add a slight excess of ammonium hydroxid. Then add by degrees t lie remaining 

 portion to ;i faint acid reaction. I". S. Kept, of Agr., Div. of (.'hem., Bui. 40 revised, p. 39. 



Wiley A: Kwell, Analyst, 1S%, -J|, 184. 



